Modern semiconductor factories use a variety of automation systems for movement of materials and control of fabrication processes. As used herein, the terms semiconductor factory and semiconductor fab are synonymous, and are respectively abbreviated as factory and fab. The various automation systems within the fab include hardware and software that are interfaced to work together to automate the movement of material, data, and control through the fab. Major automation systems in the fab may include: MES (Manufacturing Execution System), AMHS (Automated Material Handling System), MCS (Material Control System), station Control for tool connectivity, EFEMs (Equipment Front-End Modules) and loadports for interface between factory tools and the AMHS, material tracking systems like radiofrequency identifier (RFID) and barcode, and associated software products that may or may not be used in a fab and may or may not be bundled together to handle functions like fault detection, recipe management, scheduling and dispatch, statistical process control (SPC), and others.
During semiconductor manufacturing, a semiconductor wafer undergoes a plurality of process steps, each of which are performed by a specialized process tool. Pods are used to convey semiconductor wafers from one tool to another. Each pod is capable of transporting a number of wafers of a specific diameter. The pods are designed to maintain a protected internal environment to keep the wafers free of contamination, e.g., by particulates in the air outside the pod. Pods are also known for conveying other types of substrates, such as reticles, liquid crystal panels, rigid magnetic media for hard disk drives, solar cells, etc. It is an ongoing desire to improve fab logistics and productivity in the areas of cycle time, throughput, WIP (Work-In-Progress) levels, material handling, etc. It is within this context that the present invention arises.